The present invention relates to process variable transmitters of the type used to measure process variables of industrial processes. More specifically, the invention relates to reducing the impact of electrical noise sensitivity when measuring a process variable in a process variable transmitter.
Process control loops are used in various industries to control or monitor operation of industrial processes. A process variable transmitter is typically part of the process control loop and is located in the field to measure and transmit a process variable to control room equipment. The process variable can include, for example, pressure, flow, temperature, etc. Some process control loops include a controller, such as a valve controller, which is controlled in response to the process variable sensed by the transmitter.
Process transmitters are frequently used in harsh, caustic environments or in environments containing potentially explosive gasses or mixtures. Therefore, in order to reduce the possibility of damage to internal components of the transmitter from the caustic environment and of internal circuitry causing an ignition of explosive gasses, a process transmitter typically includes an electrically conductive transmitter housing which can tightly seal the internal components.
The internal components located inside the transmitter, such as, for example, internal circuitry, are connected to one another by way of wired interconnections. In industrial settings, electromagnetic fields can be generated by nearby equipment. Those fields can introduce electrical noise into electrical circuitry in the transmitter when measuring a process variable. For example, it may be the case that noise may enter the measurement circuit in the transmitter and impact measurements taken by the transmitter. This can cause unwanted errors to be transmitted by the transmitter and inaccurate readings to appear in the measurements. This may then elicit the process transmitter to transmit erroneous measurements of the process variables, causing an inability to properly monitor the operation of the underlying industrial process.